Fire can be extinguished by starving it with one or more of five factors. Efforts directs at removing the fuel is called ‘Starvation’. Depriving the fire of oxygen by dilution or by introducing other inert media is called ‘Smothering’. Cutting off the fuel vapors mixing with oxygen by applying an external media is called ‘Blanketing’ and reducing temperature is of course ‘Cooling’.
Following steps are fire extinguishing techniques:-
This method is applied by removing from the neighborhood of the fire such combustible materials as can be shifted. It is often possible to transfer coal stock or other contents from parts of a burning building to a safe place or to pump oils from tanks exposed to a fire to a remote situation.
This is an attempt to reduce the supply of oxygen necessary for continuance of the fire. A reduction of the proportion of oxygen in the atmosphere from the normal 21% to less than 15% will extinguish most fires, but in some cases the percentage of oxygen must be reduced to as low as 6%. When the burning materials e.g., celluloid includes in its chemical composition sufficient oxygen for its combustion, smothering, is of course ineffective. Inert gases or vapors may be used to displace the air surrounding a fire or by mixing with it, to reduce the oxygen content of the atmosphere to below that required for combustion to continue. Such smothering of course, a temporary one because the gases tend to be dissipated by convection currents set up by the heat of the fire, particularly in open by droughts.
Blanketing is also smothering technique. It is especially valuable in extinction of fires involving oils and other flammable liquids. Foam is frothy product to light that it will float on any liquid and form a blanket that excludes air cuts off the flames from the burning surface.
This is by far most important method of the extinction. The purpose is to reduce the temperature of the fire to below that necessary for combustion to continue. It is a matter of abstracting heat from the fire at a greater rate than it is generated, because as heat is removed the fire is progressively cooled and ultimately extinguished.
5. Breaking of Branched Chain Reaction
Fire can be extinguished by breaking or inhabiting the branched chain reaction, which occurs in the reaction zone of the flames. This can be achieved by Halogenated, Hydrocarbon, which reacts with the Hydrocarbon molecule on fire and disturbs the chain reaction and extinguishes the fire. Dry chemical powder type portable fire extinguisher acts on same principle.